llvm-project/clang/unittests/Basic/VirtualFileSystemTest.cpp

//===- unittests/Basic/VirtualFileSystem.cpp ---------------- VFS tests ---===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "clang/Basic/VirtualFileSystem.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Support/Errc.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/SourceMgr.h"
#include "gtest/gtest.h"
#include <map>

using namespace clang;
using namespace llvm;
using llvm::sys::fs::UniqueID;

namespace {
struct DummyFile : public vfs::File {
  vfs::Status S;
  explicit DummyFile(vfs::Status S) : S(S) {}
  llvm::ErrorOr<vfs::Status> status() override { return S; }
  llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
  getBuffer(const Twine &Name, int64_t FileSize, bool RequiresNullTerminator,
            bool IsVolatile) override {
    llvm_unreachable("unimplemented");
  }
  std::error_code close() override { return std::error_code(); }
};

class DummyFileSystem : public vfs::FileSystem {
  int FSID;   // used to produce UniqueIDs
  int FileID; // used to produce UniqueIDs
  std::map<std::string, vfs::Status> FilesAndDirs;

  static int getNextFSID() {
    static int Count = 0;
    return Count++;
  }

public:
  DummyFileSystem() : FSID(getNextFSID()), FileID(0) {}

  ErrorOr<vfs::Status> status(const Twine &Path) override {
    std::map<std::string, vfs::Status>::iterator I =
        FilesAndDirs.find(Path.str());
    if (I == FilesAndDirs.end())
      return make_error_code(llvm::errc::no_such_file_or_directory);
    return I->second;
  }
  ErrorOr<std::unique_ptr<vfs::File>>
  openFileForRead(const Twine &Path) override {
    auto S = status(Path);
    if (S)
      return std::unique_ptr<vfs::File>(new DummyFile{*S});
    return S.getError();
  }
  llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override {
    return std::string();
  }
  std::error_code setCurrentWorkingDirectory(const Twine &Path) override {
    return std::error_code();
  }

  struct DirIterImpl : public clang::vfs::detail::DirIterImpl {
    std::map<std::string, vfs::Status> &FilesAndDirs;
    std::map<std::string, vfs::Status>::iterator I;
    std::string Path;
    bool isInPath(StringRef S) {
      if (Path.size() < S.size() && S.find(Path) == 0) {
        auto LastSep = S.find_last_of('/');
        if (LastSep == Path.size() || LastSep == Path.size()-1)
          return true;
      }
      return false;
    }
    DirIterImpl(std::map<std::string, vfs::Status> &FilesAndDirs,
                const Twine &_Path)
        : FilesAndDirs(FilesAndDirs), I(FilesAndDirs.begin()),
          Path(_Path.str()) {
      for ( ; I != FilesAndDirs.end(); ++I) {
        if (isInPath(I->first)) {
          CurrentEntry = I->second;
          break;
        }
      }
    }
    std::error_code increment() override {
      ++I;
      for ( ; I != FilesAndDirs.end(); ++I) {
        if (isInPath(I->first)) {
          CurrentEntry = I->second;
          break;
        }
      }
      if (I == FilesAndDirs.end())
        CurrentEntry = vfs::Status();
      return std::error_code();
    }
  };

  vfs::directory_iterator dir_begin(const Twine &Dir,
                                    std::error_code &EC) override {
    return vfs::directory_iterator(
        std::make_shared<DirIterImpl>(FilesAndDirs, Dir));
  }

  void addEntry(StringRef Path, const vfs::Status &Status) {
    FilesAndDirs[Path] = Status;
  }

  void addRegularFile(StringRef Path, sys::fs::perms Perms = sys::fs::all_all) {
    vfs::Status S(Path, UniqueID(FSID, FileID++), sys::TimeValue::now(), 0, 0,
                  1024, sys::fs::file_type::regular_file, Perms);
    addEntry(Path, S);
  }

  void addDirectory(StringRef Path, sys::fs::perms Perms = sys::fs::all_all) {
    vfs::Status S(Path, UniqueID(FSID, FileID++), sys::TimeValue::now(), 0, 0,
                  0, sys::fs::file_type::directory_file, Perms);
    addEntry(Path, S);
  }

  void addSymlink(StringRef Path) {
    vfs::Status S(Path, UniqueID(FSID, FileID++), sys::TimeValue::now(), 0, 0,
                  0, sys::fs::file_type::symlink_file, sys::fs::all_all);
    addEntry(Path, S);
  }
};
} // end anonymous namespace

TEST(VirtualFileSystemTest, StatusQueries) {
  IntrusiveRefCntPtr<DummyFileSystem> D(new DummyFileSystem());
  ErrorOr<vfs::Status> Status((std::error_code()));

  D->addRegularFile("/foo");
  Status = D->status("/foo");
  ASSERT_FALSE(Status.getError());
  EXPECT_TRUE(Status->isStatusKnown());
  EXPECT_FALSE(Status->isDirectory());
  EXPECT_TRUE(Status->isRegularFile());
  EXPECT_FALSE(Status->isSymlink());
  EXPECT_FALSE(Status->isOther());
  EXPECT_TRUE(Status->exists());

  D->addDirectory("/bar");
  Status = D->status("/bar");
  ASSERT_FALSE(Status.getError());
  EXPECT_TRUE(Status->isStatusKnown());
  EXPECT_TRUE(Status->isDirectory());
  EXPECT_FALSE(Status->isRegularFile());
  EXPECT_FALSE(Status->isSymlink());
  EXPECT_FALSE(Status->isOther());
  EXPECT_TRUE(Status->exists());

  D->addSymlink("/baz");
  Status = D->status("/baz");
  ASSERT_FALSE(Status.getError());
  EXPECT_TRUE(Status->isStatusKnown());
  EXPECT_FALSE(Status->isDirectory());
  EXPECT_FALSE(Status->isRegularFile());
  EXPECT_TRUE(Status->isSymlink());
  EXPECT_FALSE(Status->isOther());
  EXPECT_TRUE(Status->exists());

  EXPECT_TRUE(Status->equivalent(*Status));
  ErrorOr<vfs::Status> Status2 = D->status("/foo");
  ASSERT_FALSE(Status2.getError());
  EXPECT_FALSE(Status->equivalent(*Status2));
}

TEST(VirtualFileSystemTest, BaseOnlyOverlay) {
  IntrusiveRefCntPtr<DummyFileSystem> D(new DummyFileSystem());
  ErrorOr<vfs::Status> Status((std::error_code()));
  EXPECT_FALSE(Status = D->status("/foo"));

  IntrusiveRefCntPtr<vfs::OverlayFileSystem> O(new vfs::OverlayFileSystem(D));
  EXPECT_FALSE(Status = O->status("/foo"));

  D->addRegularFile("/foo");
  Status = D->status("/foo");
  EXPECT_FALSE(Status.getError());

  ErrorOr<vfs::Status> Status2((std::error_code()));
  Status2 = O->status("/foo");
  EXPECT_FALSE(Status2.getError());
  EXPECT_TRUE(Status->equivalent(*Status2));
}

TEST(VirtualFileSystemTest, OverlayFiles) {
  IntrusiveRefCntPtr<DummyFileSystem> Base(new DummyFileSystem());
  IntrusiveRefCntPtr<DummyFileSystem> Middle(new DummyFileSystem());
  IntrusiveRefCntPtr<DummyFileSystem> Top(new DummyFileSystem());
  IntrusiveRefCntPtr<vfs::OverlayFileSystem> O(
      new vfs::OverlayFileSystem(Base));
  O->pushOverlay(Middle);
  O->pushOverlay(Top);

  ErrorOr<vfs::Status> Status1((std::error_code())),
      Status2((std::error_code())), Status3((std::error_code())),
      StatusB((std::error_code())), StatusM((std::error_code())),
      StatusT((std::error_code()));

  Base->addRegularFile("/foo");
  StatusB = Base->status("/foo");
  ASSERT_FALSE(StatusB.getError());
  Status1 = O->status("/foo");
  ASSERT_FALSE(Status1.getError());
  Middle->addRegularFile("/foo");
  StatusM = Middle->status("/foo");
  ASSERT_FALSE(StatusM.getError());
  Status2 = O->status("/foo");
  ASSERT_FALSE(Status2.getError());
  Top->addRegularFile("/foo");
  StatusT = Top->status("/foo");
  ASSERT_FALSE(StatusT.getError());
  Status3 = O->status("/foo");
  ASSERT_FALSE(Status3.getError());

  EXPECT_TRUE(Status1->equivalent(*StatusB));
  EXPECT_TRUE(Status2->equivalent(*StatusM));
  EXPECT_TRUE(Status3->equivalent(*StatusT));

  EXPECT_FALSE(Status1->equivalent(*Status2));
  EXPECT_FALSE(Status2->equivalent(*Status3));
  EXPECT_FALSE(Status1->equivalent(*Status3));
}

TEST(VirtualFileSystemTest, OverlayDirsNonMerged) {
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  IntrusiveRefCntPtr<DummyFileSystem> Upper(new DummyFileSystem());
  IntrusiveRefCntPtr<vfs::OverlayFileSystem> O(
      new vfs::OverlayFileSystem(Lower));
  O->pushOverlay(Upper);

  Lower->addDirectory("/lower-only");
  Upper->addDirectory("/upper-only");

  // non-merged paths should be the same
  ErrorOr<vfs::Status> Status1 = Lower->status("/lower-only");
  ASSERT_FALSE(Status1.getError());
  ErrorOr<vfs::Status> Status2 = O->status("/lower-only");
  ASSERT_FALSE(Status2.getError());
  EXPECT_TRUE(Status1->equivalent(*Status2));

  Status1 = Upper->status("/upper-only");
  ASSERT_FALSE(Status1.getError());
  Status2 = O->status("/upper-only");
  ASSERT_FALSE(Status2.getError());
  EXPECT_TRUE(Status1->equivalent(*Status2));
}

TEST(VirtualFileSystemTest, MergedDirPermissions) {
  // merged directories get the permissions of the upper dir
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  IntrusiveRefCntPtr<DummyFileSystem> Upper(new DummyFileSystem());
  IntrusiveRefCntPtr<vfs::OverlayFileSystem> O(
      new vfs::OverlayFileSystem(Lower));
  O->pushOverlay(Upper);

  ErrorOr<vfs::Status> Status((std::error_code()));
  Lower->addDirectory("/both", sys::fs::owner_read);
  Upper->addDirectory("/both", sys::fs::owner_all | sys::fs::group_read);
  Status = O->status("/both");
  ASSERT_FALSE(Status.getError());
  EXPECT_EQ(0740, Status->getPermissions());

  // permissions (as usual) are not recursively applied
  Lower->addRegularFile("/both/foo", sys::fs::owner_read);
  Upper->addRegularFile("/both/bar", sys::fs::owner_write);
  Status = O->status("/both/foo");
  ASSERT_FALSE( Status.getError());
  EXPECT_EQ(0400, Status->getPermissions());
  Status = O->status("/both/bar");
  ASSERT_FALSE(Status.getError());
  EXPECT_EQ(0200, Status->getPermissions());
}

namespace {
struct ScopedDir {
  SmallString<128> Path;
  ScopedDir(const Twine &Name, bool Unique=false) {
    std::error_code EC;
    if (Unique) {
      EC =  llvm::sys::fs::createUniqueDirectory(Name, Path);
    } else {
      Path = Name.str();
      EC = llvm::sys::fs::create_directory(Twine(Path));
    }
    if (EC)
      Path = "";
    EXPECT_FALSE(EC);
  }
  ~ScopedDir() {
    if (Path != "")
      EXPECT_FALSE(llvm::sys::fs::remove(Path.str()));
  }
  operator StringRef() { return Path.str(); }
};
} // end anonymous namespace

TEST(VirtualFileSystemTest, BasicRealFSIteration) {
  ScopedDir TestDirectory("virtual-file-system-test", /*Unique*/true);
  IntrusiveRefCntPtr<vfs::FileSystem> FS = vfs::getRealFileSystem();

  std::error_code EC;
  vfs::directory_iterator I = FS->dir_begin(Twine(TestDirectory), EC);
  ASSERT_FALSE(EC);
  EXPECT_EQ(vfs::directory_iterator(), I); // empty directory is empty

  ScopedDir _a(TestDirectory+"/a");
  ScopedDir _ab(TestDirectory+"/a/b");
  ScopedDir _c(TestDirectory+"/c");
  ScopedDir _cd(TestDirectory+"/c/d");

  I = FS->dir_begin(Twine(TestDirectory), EC);
  ASSERT_FALSE(EC);
  ASSERT_NE(vfs::directory_iterator(), I);
  // Check either a or c, since we can't rely on the iteration order.
  EXPECT_TRUE(I->getName().endswith("a") || I->getName().endswith("c"));
  I.increment(EC);
  ASSERT_FALSE(EC);
  ASSERT_NE(vfs::directory_iterator(), I);
  EXPECT_TRUE(I->getName().endswith("a") || I->getName().endswith("c"));
  I.increment(EC);
  EXPECT_EQ(vfs::directory_iterator(), I);
}

TEST(VirtualFileSystemTest, BasicRealFSRecursiveIteration) {
  ScopedDir TestDirectory("virtual-file-system-test", /*Unique*/true);
  IntrusiveRefCntPtr<vfs::FileSystem> FS = vfs::getRealFileSystem();

  std::error_code EC;
  auto I = vfs::recursive_directory_iterator(*FS, Twine(TestDirectory), EC);
  ASSERT_FALSE(EC);
  EXPECT_EQ(vfs::recursive_directory_iterator(), I); // empty directory is empty

  ScopedDir _a(TestDirectory+"/a");
  ScopedDir _ab(TestDirectory+"/a/b");
  ScopedDir _c(TestDirectory+"/c");
  ScopedDir _cd(TestDirectory+"/c/d");

  I = vfs::recursive_directory_iterator(*FS, Twine(TestDirectory), EC);
  ASSERT_FALSE(EC);
  ASSERT_NE(vfs::recursive_directory_iterator(), I);

  std::vector<std::string> Contents;
  for (auto E = vfs::recursive_directory_iterator(); !EC && I != E;
       I.increment(EC)) {
    Contents.push_back(I->getName());
  }

  // Check contents, which may be in any order
  EXPECT_EQ(4U, Contents.size());
  int Counts[4] = { 0, 0, 0, 0 };
  for (const std::string &Name : Contents) {
    ASSERT_FALSE(Name.empty());
    int Index = Name[Name.size()-1] - 'a';
    ASSERT_TRUE(Index >= 0 && Index < 4);
    Counts[Index]++;
  }
  EXPECT_EQ(1, Counts[0]); // a
  EXPECT_EQ(1, Counts[1]); // b
  EXPECT_EQ(1, Counts[2]); // c
  EXPECT_EQ(1, Counts[3]); // d
}

template <typename DirIter>
static void checkContents(DirIter I, ArrayRef<StringRef> ExpectedOut) {
  std::error_code EC;
  SmallVector<StringRef, 4> Expected(ExpectedOut.begin(), ExpectedOut.end());
  SmallVector<std::string, 4> InputToCheck;

  // Do not rely on iteration order to check for contents, sort both
  // content vectors before comparison.
  for (DirIter E; !EC && I != E; I.increment(EC))
    InputToCheck.push_back(I->getName());

  std::sort(InputToCheck.begin(), InputToCheck.end());
  std::sort(Expected.begin(), Expected.end());
  EXPECT_EQ(InputToCheck.size(), Expected.size());

  unsigned LastElt = std::min(InputToCheck.size(), Expected.size());
  for (unsigned Idx = 0; Idx != LastElt; ++Idx)
    EXPECT_EQ(StringRef(InputToCheck[Idx]), Expected[Idx]);
}

TEST(VirtualFileSystemTest, OverlayIteration) {
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  IntrusiveRefCntPtr<DummyFileSystem> Upper(new DummyFileSystem());
  IntrusiveRefCntPtr<vfs::OverlayFileSystem> O(
      new vfs::OverlayFileSystem(Lower));
  O->pushOverlay(Upper);

  std::error_code EC;
  checkContents(O->dir_begin("/", EC), ArrayRef<StringRef>());

  Lower->addRegularFile("/file1");
  checkContents(O->dir_begin("/", EC), ArrayRef<StringRef>("/file1"));

  Upper->addRegularFile("/file2");
  checkContents(O->dir_begin("/", EC), {"/file2", "/file1"});

  Lower->addDirectory("/dir1");
  Lower->addRegularFile("/dir1/foo");
  Upper->addDirectory("/dir2");
  Upper->addRegularFile("/dir2/foo");
  checkContents(O->dir_begin("/dir2", EC), ArrayRef<StringRef>("/dir2/foo"));
  checkContents(O->dir_begin("/", EC), {"/dir2", "/file2", "/dir1", "/file1"});
}

TEST(VirtualFileSystemTest, OverlayRecursiveIteration) {
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  IntrusiveRefCntPtr<DummyFileSystem> Middle(new DummyFileSystem());
  IntrusiveRefCntPtr<DummyFileSystem> Upper(new DummyFileSystem());
  IntrusiveRefCntPtr<vfs::OverlayFileSystem> O(
      new vfs::OverlayFileSystem(Lower));
  O->pushOverlay(Middle);
  O->pushOverlay(Upper);

  std::error_code EC;
  checkContents(vfs::recursive_directory_iterator(*O, "/", EC),
                ArrayRef<StringRef>());

  Lower->addRegularFile("/file1");
  checkContents(vfs::recursive_directory_iterator(*O, "/", EC),
                ArrayRef<StringRef>("/file1"));

  Upper->addDirectory("/dir");
  Upper->addRegularFile("/dir/file2");
  checkContents(vfs::recursive_directory_iterator(*O, "/", EC),
                {"/dir", "/dir/file2", "/file1"});

  Lower->addDirectory("/dir1");
  Lower->addRegularFile("/dir1/foo");
  Lower->addDirectory("/dir1/a");
  Lower->addRegularFile("/dir1/a/b");
  Middle->addDirectory("/a");
  Middle->addDirectory("/a/b");
  Middle->addDirectory("/a/b/c");
  Middle->addRegularFile("/a/b/c/d");
  Middle->addRegularFile("/hiddenByUp");
  Upper->addDirectory("/dir2");
  Upper->addRegularFile("/dir2/foo");
  Upper->addRegularFile("/hiddenByUp");
  checkContents(vfs::recursive_directory_iterator(*O, "/dir2", EC),
                ArrayRef<StringRef>("/dir2/foo"));
  checkContents(vfs::recursive_directory_iterator(*O, "/", EC),
                {"/dir", "/dir/file2", "/dir2", "/dir2/foo", "/hiddenByUp",
                 "/a", "/a/b", "/a/b/c", "/a/b/c/d", "/dir1", "/dir1/a",
                 "/dir1/a/b", "/dir1/foo", "/file1"});
}

TEST(VirtualFileSystemTest, ThreeLevelIteration) {
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  IntrusiveRefCntPtr<DummyFileSystem> Middle(new DummyFileSystem());
  IntrusiveRefCntPtr<DummyFileSystem> Upper(new DummyFileSystem());
  IntrusiveRefCntPtr<vfs::OverlayFileSystem> O(
      new vfs::OverlayFileSystem(Lower));
  O->pushOverlay(Middle);
  O->pushOverlay(Upper);

  std::error_code EC;
  checkContents(O->dir_begin("/", EC), ArrayRef<StringRef>());

  Middle->addRegularFile("/file2");
  checkContents(O->dir_begin("/", EC), ArrayRef<StringRef>("/file2"));

  Lower->addRegularFile("/file1");
  Upper->addRegularFile("/file3");
  checkContents(O->dir_begin("/", EC), {"/file3", "/file2", "/file1"});
}

TEST(VirtualFileSystemTest, HiddenInIteration) {
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  IntrusiveRefCntPtr<DummyFileSystem> Middle(new DummyFileSystem());
  IntrusiveRefCntPtr<DummyFileSystem> Upper(new DummyFileSystem());
  IntrusiveRefCntPtr<vfs::OverlayFileSystem> O(
      new vfs::OverlayFileSystem(Lower));
  O->pushOverlay(Middle);
  O->pushOverlay(Upper);

  std::error_code EC;
  Lower->addRegularFile("/onlyInLow", sys::fs::owner_read);
  Lower->addRegularFile("/hiddenByMid", sys::fs::owner_read);
  Lower->addRegularFile("/hiddenByUp", sys::fs::owner_read);
  Middle->addRegularFile("/onlyInMid", sys::fs::owner_write);
  Middle->addRegularFile("/hiddenByMid", sys::fs::owner_write);
  Middle->addRegularFile("/hiddenByUp", sys::fs::owner_write);
  Upper->addRegularFile("/onlyInUp", sys::fs::owner_all);
  Upper->addRegularFile("/hiddenByUp", sys::fs::owner_all);
  checkContents(
      O->dir_begin("/", EC),
      {"/hiddenByUp", "/onlyInUp", "/hiddenByMid", "/onlyInMid", "/onlyInLow"});

  // Make sure we get the top-most entry
  {
    std::error_code EC;
    vfs::directory_iterator I = O->dir_begin("/", EC), E;
    for ( ; !EC && I != E; I.increment(EC))
      if (I->getName() == "/hiddenByUp")
        break;
    ASSERT_NE(E, I);
    EXPECT_EQ(sys::fs::owner_all, I->getPermissions());
  }
  {
    std::error_code EC;
    vfs::directory_iterator I = O->dir_begin("/", EC), E;
    for ( ; !EC && I != E; I.increment(EC))
      if (I->getName() == "/hiddenByMid")
        break;
    ASSERT_NE(E, I);
    EXPECT_EQ(sys::fs::owner_write, I->getPermissions());
  }
}

class InMemoryFileSystemTest : public ::testing::Test {
protected:
  clang::vfs::InMemoryFileSystem FS;
  clang::vfs::InMemoryFileSystem NormalizedFS;

  InMemoryFileSystemTest()
      : FS(/*UseNormalizedPaths=*/false),
        NormalizedFS(/*UseNormalizedPaths=*/true) {}
};

TEST_F(InMemoryFileSystemTest, IsEmpty) {
  auto Stat = FS.status("/a");
  ASSERT_EQ(Stat.getError(),errc::no_such_file_or_directory) << FS.toString();
  Stat = FS.status("/");
  ASSERT_EQ(Stat.getError(), errc::no_such_file_or_directory) << FS.toString();
}

TEST_F(InMemoryFileSystemTest, WindowsPath) {
  FS.addFile("c:/windows/system128/foo.cpp", 0, MemoryBuffer::getMemBuffer(""));
  auto Stat = FS.status("c:");
#if !defined(_WIN32)
  ASSERT_FALSE(Stat.getError()) << Stat.getError() << FS.toString();
#endif
  Stat = FS.status("c:/windows/system128/foo.cpp");
  ASSERT_FALSE(Stat.getError()) << Stat.getError() << FS.toString();
  FS.addFile("d:/windows/foo.cpp", 0, MemoryBuffer::getMemBuffer(""));
  Stat = FS.status("d:/windows/foo.cpp");
  ASSERT_FALSE(Stat.getError()) << Stat.getError() << FS.toString();
}

TEST_F(InMemoryFileSystemTest, OverlayFile) {
  FS.addFile("/a", 0, MemoryBuffer::getMemBuffer("a"));
  NormalizedFS.addFile("/a", 0, MemoryBuffer::getMemBuffer("a"));
  auto Stat = FS.status("/");
  ASSERT_FALSE(Stat.getError()) << Stat.getError() << FS.toString();
  Stat = FS.status("/.");
  ASSERT_FALSE(Stat);
  Stat = NormalizedFS.status("/.");
  ASSERT_FALSE(Stat.getError()) << Stat.getError() << FS.toString();
  Stat = FS.status("/a");
  ASSERT_FALSE(Stat.getError()) << Stat.getError() << "\n" << FS.toString();
  ASSERT_EQ("/a", Stat->getName());
}

TEST_F(InMemoryFileSystemTest, OverlayFileNoOwn) {
  auto Buf = MemoryBuffer::getMemBuffer("a");
  FS.addFileNoOwn("/a", 0, Buf.get());
  auto Stat = FS.status("/a");
  ASSERT_FALSE(Stat.getError()) << Stat.getError() << "\n" << FS.toString();
  ASSERT_EQ("/a", Stat->getName());
}

TEST_F(InMemoryFileSystemTest, OpenFileForRead) {
  FS.addFile("/a", 0, MemoryBuffer::getMemBuffer("a"));
  FS.addFile("././c", 0, MemoryBuffer::getMemBuffer("c"));
  FS.addFile("./d/../d", 0, MemoryBuffer::getMemBuffer("d"));
  NormalizedFS.addFile("/a", 0, MemoryBuffer::getMemBuffer("a"));
  NormalizedFS.addFile("././c", 0, MemoryBuffer::getMemBuffer("c"));
  NormalizedFS.addFile("./d/../d", 0, MemoryBuffer::getMemBuffer("d"));
  auto File = FS.openFileForRead("/a");
  ASSERT_EQ("a", (*(*File)->getBuffer("ignored"))->getBuffer());
  File = FS.openFileForRead("/a"); // Open again.
  ASSERT_EQ("a", (*(*File)->getBuffer("ignored"))->getBuffer());
  File = NormalizedFS.openFileForRead("/././a"); // Open again.
  ASSERT_EQ("a", (*(*File)->getBuffer("ignored"))->getBuffer());
  File = FS.openFileForRead("/");
  ASSERT_EQ(File.getError(), errc::invalid_argument) << FS.toString();
  File = FS.openFileForRead("/b");
  ASSERT_EQ(File.getError(), errc::no_such_file_or_directory) << FS.toString();
  File = FS.openFileForRead("./c");
  ASSERT_FALSE(File);
  File = FS.openFileForRead("e/../d");
  ASSERT_FALSE(File);
  File = NormalizedFS.openFileForRead("./c");
  ASSERT_EQ("c", (*(*File)->getBuffer("ignored"))->getBuffer());
  File = NormalizedFS.openFileForRead("e/../d");
  ASSERT_EQ("d", (*(*File)->getBuffer("ignored"))->getBuffer());
}

TEST_F(InMemoryFileSystemTest, DuplicatedFile) {
  ASSERT_TRUE(FS.addFile("/a", 0, MemoryBuffer::getMemBuffer("a")));
  ASSERT_FALSE(FS.addFile("/a/b", 0, MemoryBuffer::getMemBuffer("a")));
  ASSERT_TRUE(FS.addFile("/a", 0, MemoryBuffer::getMemBuffer("a")));
  ASSERT_FALSE(FS.addFile("/a", 0, MemoryBuffer::getMemBuffer("b")));
}

TEST_F(InMemoryFileSystemTest, DirectoryIteration) {
  FS.addFile("/a", 0, MemoryBuffer::getMemBuffer(""));
  FS.addFile("/b/c", 0, MemoryBuffer::getMemBuffer(""));

  std::error_code EC;
  vfs::directory_iterator I = FS.dir_begin("/", EC);
  ASSERT_FALSE(EC);
  ASSERT_EQ("/a", I->getName());
  I.increment(EC);
  ASSERT_FALSE(EC);
  ASSERT_EQ("/b", I->getName());
  I.increment(EC);
  ASSERT_FALSE(EC);
  ASSERT_EQ(vfs::directory_iterator(), I);

  I = FS.dir_begin("/b", EC);
  ASSERT_FALSE(EC);
  ASSERT_EQ("/b/c", I->getName());
  I.increment(EC);
  ASSERT_FALSE(EC);
  ASSERT_EQ(vfs::directory_iterator(), I);
}

TEST_F(InMemoryFileSystemTest, WorkingDirectory) {
  FS.setCurrentWorkingDirectory("/b");
  FS.addFile("c", 0, MemoryBuffer::getMemBuffer(""));

  auto Stat = FS.status("/b/c");
  ASSERT_FALSE(Stat.getError()) << Stat.getError() << "\n" << FS.toString();
  ASSERT_EQ("c", Stat->getName());
  ASSERT_EQ("/b", *FS.getCurrentWorkingDirectory());

  Stat = FS.status("c");
  ASSERT_FALSE(Stat.getError()) << Stat.getError() << "\n" << FS.toString();

  auto ReplaceBackslashes = [](std::string S) {
    std::replace(S.begin(), S.end(), '\\', '/');
    return S;
  };
  NormalizedFS.setCurrentWorkingDirectory("/b/c");
  NormalizedFS.setCurrentWorkingDirectory(".");
  ASSERT_EQ("/b/c", ReplaceBackslashes(
                        NormalizedFS.getCurrentWorkingDirectory().get()));
  NormalizedFS.setCurrentWorkingDirectory("..");
  ASSERT_EQ("/b", ReplaceBackslashes(
                      NormalizedFS.getCurrentWorkingDirectory().get()));
}

// NOTE: in the tests below, we use '//root/' as our root directory, since it is
// a legal *absolute* path on Windows as well as *nix.
class VFSFromYAMLTest : public ::testing::Test {
public:
  int NumDiagnostics;

  void SetUp() override { NumDiagnostics = 0; }

  static void CountingDiagHandler(const SMDiagnostic &, void *Context) {
    VFSFromYAMLTest *Test = static_cast<VFSFromYAMLTest *>(Context);
    ++Test->NumDiagnostics;
  }

  IntrusiveRefCntPtr<vfs::FileSystem>
  getFromYAMLRawString(StringRef Content,
                       IntrusiveRefCntPtr<vfs::FileSystem> ExternalFS) {
    std::unique_ptr<MemoryBuffer> Buffer = MemoryBuffer::getMemBuffer(Content);
    return getVFSFromYAML(std::move(Buffer), CountingDiagHandler, "", this,
                          ExternalFS);
  }

  IntrusiveRefCntPtr<vfs::FileSystem> getFromYAMLString(
      StringRef Content,
      IntrusiveRefCntPtr<vfs::FileSystem> ExternalFS = new DummyFileSystem()) {
    std::string VersionPlusContent("{\n  'version':0,\n");
    VersionPlusContent += Content.slice(Content.find('{') + 1, StringRef::npos);
    return getFromYAMLRawString(VersionPlusContent, ExternalFS);
  }

  // This is intended as a "XFAIL" for windows hosts.
  bool supportsSameDirMultipleYAMLEntries() {
    Triple Host(Triple::normalize(sys::getProcessTriple()));
    return !Host.isOSWindows();
  }
};

TEST_F(VFSFromYAMLTest, BasicVFSFromYAML) {
  IntrusiveRefCntPtr<vfs::FileSystem> FS;
  FS = getFromYAMLString("");
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLString("[]");
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLString("'string'");
  EXPECT_EQ(nullptr, FS.get());
  EXPECT_EQ(3, NumDiagnostics);
}

TEST_F(VFSFromYAMLTest, MappedFiles) {
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  Lower->addRegularFile("//root/foo/bar/a");
  IntrusiveRefCntPtr<vfs::FileSystem> FS =
      getFromYAMLString("{ 'roots': [\n"
                        "{\n"
                        "  'type': 'directory',\n"
                        "  'name': '//root/',\n"
                        "  'contents': [ {\n"
                        "                  'type': 'file',\n"
                        "                  'name': 'file1',\n"
                        "                  'external-contents': '//root/foo/bar/a'\n"
                        "                },\n"
                        "                {\n"
                        "                  'type': 'file',\n"
                        "                  'name': 'file2',\n"
                        "                  'external-contents': '//root/foo/b'\n"
                        "                }\n"
                        "              ]\n"
                        "}\n"
                        "]\n"
                        "}",
                        Lower);
  ASSERT_TRUE(FS.get() != nullptr);

  IntrusiveRefCntPtr<vfs::OverlayFileSystem> O(
      new vfs::OverlayFileSystem(Lower));
  O->pushOverlay(FS);

  // file
  ErrorOr<vfs::Status> S = O->status("//root/file1");
  ASSERT_FALSE(S.getError());
  EXPECT_EQ("//root/foo/bar/a", S->getName());
  EXPECT_TRUE(S->IsVFSMapped);

  ErrorOr<vfs::Status> SLower = O->status("//root/foo/bar/a");
  EXPECT_EQ("//root/foo/bar/a", SLower->getName());
  EXPECT_TRUE(S->equivalent(*SLower));
  EXPECT_FALSE(SLower->IsVFSMapped);

  // file after opening
  auto OpenedF = O->openFileForRead("//root/file1");
  ASSERT_FALSE(OpenedF.getError());
  auto OpenedS = (*OpenedF)->status();
  ASSERT_FALSE(OpenedS.getError());
  EXPECT_EQ("//root/foo/bar/a", OpenedS->getName());
  EXPECT_TRUE(OpenedS->IsVFSMapped);

  // directory
  S = O->status("//root/");
  ASSERT_FALSE(S.getError());
  EXPECT_TRUE(S->isDirectory());
  EXPECT_TRUE(S->equivalent(*O->status("//root/"))); // non-volatile UniqueID

  // broken mapping
  EXPECT_EQ(O->status("//root/file2").getError(),
            llvm::errc::no_such_file_or_directory);
  EXPECT_EQ(0, NumDiagnostics);
}

TEST_F(VFSFromYAMLTest, CaseInsensitive) {
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  Lower->addRegularFile("//root/foo/bar/a");
  IntrusiveRefCntPtr<vfs::FileSystem> FS =
      getFromYAMLString("{ 'case-sensitive': 'false',\n"
                        "  'roots': [\n"
                        "{\n"
                        "  'type': 'directory',\n"
                        "  'name': '//root/',\n"
                        "  'contents': [ {\n"
                        "                  'type': 'file',\n"
                        "                  'name': 'XX',\n"
                        "                  'external-contents': '//root/foo/bar/a'\n"
                        "                }\n"
                        "              ]\n"
                        "}]}",
                        Lower);
  ASSERT_TRUE(FS.get() != nullptr);

  IntrusiveRefCntPtr<vfs::OverlayFileSystem> O(
      new vfs::OverlayFileSystem(Lower));
  O->pushOverlay(FS);

  ErrorOr<vfs::Status> S = O->status("//root/XX");
  ASSERT_FALSE(S.getError());

  ErrorOr<vfs::Status> SS = O->status("//root/xx");
  ASSERT_FALSE(SS.getError());
  EXPECT_TRUE(S->equivalent(*SS));
  SS = O->status("//root/xX");
  EXPECT_TRUE(S->equivalent(*SS));
  SS = O->status("//root/Xx");
  EXPECT_TRUE(S->equivalent(*SS));
  EXPECT_EQ(0, NumDiagnostics);
}

TEST_F(VFSFromYAMLTest, CaseSensitive) {
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  Lower->addRegularFile("//root/foo/bar/a");
  IntrusiveRefCntPtr<vfs::FileSystem> FS =
      getFromYAMLString("{ 'case-sensitive': 'true',\n"
                        "  'roots': [\n"
                        "{\n"
                        "  'type': 'directory',\n"
                        "  'name': '//root/',\n"
                        "  'contents': [ {\n"
                        "                  'type': 'file',\n"
                        "                  'name': 'XX',\n"
                        "                  'external-contents': '//root/foo/bar/a'\n"
                        "                }\n"
                        "              ]\n"
                        "}]}",
                        Lower);
  ASSERT_TRUE(FS.get() != nullptr);

  IntrusiveRefCntPtr<vfs::OverlayFileSystem> O(
      new vfs::OverlayFileSystem(Lower));
  O->pushOverlay(FS);

  ErrorOr<vfs::Status> SS = O->status("//root/xx");
  EXPECT_EQ(SS.getError(), llvm::errc::no_such_file_or_directory);
  SS = O->status("//root/xX");
  EXPECT_EQ(SS.getError(), llvm::errc::no_such_file_or_directory);
  SS = O->status("//root/Xx");
  EXPECT_EQ(SS.getError(), llvm::errc::no_such_file_or_directory);
  EXPECT_EQ(0, NumDiagnostics);
}

TEST_F(VFSFromYAMLTest, IllegalVFSFile) {
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());

  // invalid YAML at top-level
  IntrusiveRefCntPtr<vfs::FileSystem> FS = getFromYAMLString("{]", Lower);
  EXPECT_EQ(nullptr, FS.get());
  // invalid YAML in roots
  FS = getFromYAMLString("{ 'roots':[}", Lower);
  // invalid YAML in directory
  FS = getFromYAMLString(
      "{ 'roots':[ { 'name': 'foo', 'type': 'directory', 'contents': [}",
      Lower);
  EXPECT_EQ(nullptr, FS.get());

  // invalid configuration
  FS = getFromYAMLString("{ 'knobular': 'true', 'roots':[] }", Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLString("{ 'case-sensitive': 'maybe', 'roots':[] }", Lower);
  EXPECT_EQ(nullptr, FS.get());

  // invalid roots
  FS = getFromYAMLString("{ 'roots':'' }", Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLString("{ 'roots':{} }", Lower);
  EXPECT_EQ(nullptr, FS.get());

  // invalid entries
  FS = getFromYAMLString(
      "{ 'roots':[ { 'type': 'other', 'name': 'me', 'contents': '' }", Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLString("{ 'roots':[ { 'type': 'file', 'name': [], "
                         "'external-contents': 'other' }",
                         Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLString(
      "{ 'roots':[ { 'type': 'file', 'name': 'me', 'external-contents': [] }",
      Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLString(
      "{ 'roots':[ { 'type': 'file', 'name': 'me', 'external-contents': {} }",
      Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLString(
      "{ 'roots':[ { 'type': 'directory', 'name': 'me', 'contents': {} }",
      Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLString(
      "{ 'roots':[ { 'type': 'directory', 'name': 'me', 'contents': '' }",
      Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLString(
      "{ 'roots':[ { 'thingy': 'directory', 'name': 'me', 'contents': [] }",
      Lower);
  EXPECT_EQ(nullptr, FS.get());

  // missing mandatory fields
  FS = getFromYAMLString("{ 'roots':[ { 'type': 'file', 'name': 'me' }", Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLString(
      "{ 'roots':[ { 'type': 'file', 'external-contents': 'other' }", Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLString("{ 'roots':[ { 'name': 'me', 'contents': [] }", Lower);
  EXPECT_EQ(nullptr, FS.get());

  // duplicate keys
  FS = getFromYAMLString("{ 'roots':[], 'roots':[] }", Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLString(
      "{ 'case-sensitive':'true', 'case-sensitive':'true', 'roots':[] }",
      Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS =
      getFromYAMLString("{ 'roots':[{'name':'me', 'name':'you', 'type':'file', "
                        "'external-contents':'blah' } ] }",
                        Lower);
  EXPECT_EQ(nullptr, FS.get());

  // missing version
  FS = getFromYAMLRawString("{ 'roots':[] }", Lower);
  EXPECT_EQ(nullptr, FS.get());

  // bad version number
  FS = getFromYAMLRawString("{ 'version':'foo', 'roots':[] }", Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLRawString("{ 'version':-1, 'roots':[] }", Lower);
  EXPECT_EQ(nullptr, FS.get());
  FS = getFromYAMLRawString("{ 'version':100000, 'roots':[] }", Lower);
  EXPECT_EQ(nullptr, FS.get());
  EXPECT_EQ(24, NumDiagnostics);
}

TEST_F(VFSFromYAMLTest, UseExternalName) {
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  Lower->addRegularFile("//root/external/file");

  IntrusiveRefCntPtr<vfs::FileSystem> FS = getFromYAMLString(
      "{ 'roots': [\n"
      "  { 'type': 'file', 'name': '//root/A',\n"
      "    'external-contents': '//root/external/file'\n"
      "  },\n"
      "  { 'type': 'file', 'name': '//root/B',\n"
      "    'use-external-name': true,\n"
      "    'external-contents': '//root/external/file'\n"
      "  },\n"
      "  { 'type': 'file', 'name': '//root/C',\n"
      "    'use-external-name': false,\n"
      "    'external-contents': '//root/external/file'\n"
      "  }\n"
      "] }", Lower);
  ASSERT_TRUE(nullptr != FS.get());

  // default true
  EXPECT_EQ("//root/external/file", FS->status("//root/A")->getName());
  // explicit
  EXPECT_EQ("//root/external/file", FS->status("//root/B")->getName());
  EXPECT_EQ("//root/C", FS->status("//root/C")->getName());

  // global configuration
  FS = getFromYAMLString(
      "{ 'use-external-names': false,\n"
      "  'roots': [\n"
      "  { 'type': 'file', 'name': '//root/A',\n"
      "    'external-contents': '//root/external/file'\n"
      "  },\n"
      "  { 'type': 'file', 'name': '//root/B',\n"
      "    'use-external-name': true,\n"
      "    'external-contents': '//root/external/file'\n"
      "  },\n"
      "  { 'type': 'file', 'name': '//root/C',\n"
      "    'use-external-name': false,\n"
      "    'external-contents': '//root/external/file'\n"
      "  }\n"
      "] }", Lower);
  ASSERT_TRUE(nullptr != FS.get());

  // default
  EXPECT_EQ("//root/A", FS->status("//root/A")->getName());
  // explicit
  EXPECT_EQ("//root/external/file", FS->status("//root/B")->getName());
  EXPECT_EQ("//root/C", FS->status("//root/C")->getName());
}

TEST_F(VFSFromYAMLTest, MultiComponentPath) {
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  Lower->addRegularFile("//root/other");

  // file in roots
  IntrusiveRefCntPtr<vfs::FileSystem> FS = getFromYAMLString(
      "{ 'roots': [\n"
      "  { 'type': 'file', 'name': '//root/path/to/file',\n"
      "    'external-contents': '//root/other' }]\n"
      "}", Lower);
  ASSERT_TRUE(nullptr != FS.get());
  EXPECT_FALSE(FS->status("//root/path/to/file").getError());
  EXPECT_FALSE(FS->status("//root/path/to").getError());
  EXPECT_FALSE(FS->status("//root/path").getError());
  EXPECT_FALSE(FS->status("//root/").getError());

  // at the start
  FS = getFromYAMLString(
      "{ 'roots': [\n"
      "  { 'type': 'directory', 'name': '//root/path/to',\n"
      "    'contents': [ { 'type': 'file', 'name': 'file',\n"
      "                    'external-contents': '//root/other' }]}]\n"
      "}", Lower);
  ASSERT_TRUE(nullptr != FS.get());
  EXPECT_FALSE(FS->status("//root/path/to/file").getError());
  EXPECT_FALSE(FS->status("//root/path/to").getError());
  EXPECT_FALSE(FS->status("//root/path").getError());
  EXPECT_FALSE(FS->status("//root/").getError());

  // at the end
  FS = getFromYAMLString(
      "{ 'roots': [\n"
      "  { 'type': 'directory', 'name': '//root/',\n"
      "    'contents': [ { 'type': 'file', 'name': 'path/to/file',\n"
      "                    'external-contents': '//root/other' }]}]\n"
      "}", Lower);
  ASSERT_TRUE(nullptr != FS.get());
  EXPECT_FALSE(FS->status("//root/path/to/file").getError());
  EXPECT_FALSE(FS->status("//root/path/to").getError());
  EXPECT_FALSE(FS->status("//root/path").getError());
  EXPECT_FALSE(FS->status("//root/").getError());
}

TEST_F(VFSFromYAMLTest, TrailingSlashes) {
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  Lower->addRegularFile("//root/other");

  // file in roots
  IntrusiveRefCntPtr<vfs::FileSystem> FS = getFromYAMLString(
      "{ 'roots': [\n"
      "  { 'type': 'directory', 'name': '//root/path/to////',\n"
      "    'contents': [ { 'type': 'file', 'name': 'file',\n"
      "                    'external-contents': '//root/other' }]}]\n"
      "}", Lower);
  ASSERT_TRUE(nullptr != FS.get());
  EXPECT_FALSE(FS->status("//root/path/to/file").getError());
  EXPECT_FALSE(FS->status("//root/path/to").getError());
  EXPECT_FALSE(FS->status("//root/path").getError());
  EXPECT_FALSE(FS->status("//root/").getError());
}

TEST_F(VFSFromYAMLTest, DirectoryIteration) {
  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  Lower->addDirectory("//root/");
  Lower->addDirectory("//root/foo");
  Lower->addDirectory("//root/foo/bar");
  Lower->addRegularFile("//root/foo/bar/a");
  Lower->addRegularFile("//root/foo/bar/b");
  Lower->addRegularFile("//root/file3");
  IntrusiveRefCntPtr<vfs::FileSystem> FS =
  getFromYAMLString("{ 'use-external-names': false,\n"
                    "  'roots': [\n"
                    "{\n"
                    "  'type': 'directory',\n"
                    "  'name': '//root/',\n"
                    "  'contents': [ {\n"
                    "                  'type': 'file',\n"
                    "                  'name': 'file1',\n"
                    "                  'external-contents': '//root/foo/bar/a'\n"
                    "                },\n"
                    "                {\n"
                    "                  'type': 'file',\n"
                    "                  'name': 'file2',\n"
                    "                  'external-contents': '//root/foo/bar/b'\n"
                    "                }\n"
                    "              ]\n"
                    "}\n"
                    "]\n"
                    "}",
                    Lower);
  ASSERT_TRUE(FS.get() != nullptr);

  IntrusiveRefCntPtr<vfs::OverlayFileSystem> O(
      new vfs::OverlayFileSystem(Lower));
  O->pushOverlay(FS);

  std::error_code EC;
  checkContents(O->dir_begin("//root/", EC),
                {"//root/file1", "//root/file2", "//root/file3", "//root/foo"});

  checkContents(O->dir_begin("//root/foo/bar", EC),
                {"//root/foo/bar/a", "//root/foo/bar/b"});
}

TEST_F(VFSFromYAMLTest, DirectoryIterationSameDirMultipleEntries) {
  // https://llvm.org/bugs/show_bug.cgi?id=27725
  if (!supportsSameDirMultipleYAMLEntries())
    return;

  IntrusiveRefCntPtr<DummyFileSystem> Lower(new DummyFileSystem());
  Lower->addDirectory("//root/zab");
  Lower->addDirectory("//root/baz");
  Lower->addRegularFile("//root/zab/a");
  Lower->addRegularFile("//root/zab/b");
  IntrusiveRefCntPtr<vfs::FileSystem> FS = getFromYAMLString(
      "{ 'use-external-names': false,\n"
      "  'roots': [\n"
      "{\n"
      "  'type': 'directory',\n"
      "  'name': '//root/baz/',\n"
      "  'contents': [ {\n"
      "                  'type': 'file',\n"
      "                  'name': 'x',\n"
      "                  'external-contents': '//root/zab/a'\n"
      "                }\n"
      "              ]\n"
      "},\n"
      "{\n"
      "  'type': 'directory',\n"
      "  'name': '//root/baz/',\n"
      "  'contents': [ {\n"
      "                  'type': 'file',\n"
      "                  'name': 'y',\n"
      "                  'external-contents': '//root/zab/b'\n"
      "                }\n"
      "              ]\n"
      "}\n"
      "]\n"
      "}",
      Lower);
  ASSERT_TRUE(FS.get() != nullptr);

  IntrusiveRefCntPtr<vfs::OverlayFileSystem> O(
      new vfs::OverlayFileSystem(Lower));
  O->pushOverlay(FS);

  std::error_code EC;

  checkContents(O->dir_begin("//root/baz/", EC),
                {"//root/baz/x", "//root/baz/y"});
}